The valve assembly of the invention finds particular although not exclusive application in solar panel installation systems. In such installation systems, a problem occurs when the system is filled with water or drained. Recurring filling and draining operations are required, for example, in environments where a likelihood of freezing exists. During the filling of a typical solar panel installation, the high point in the system has a tendency to trap air. It is essential, however, that such air be vented out of the system to assure efficient operation of the system with a maximum amount of liquid. Moreover, when a typical solar panel installation is drained, there is a tendency for vacuum to be created in the system which slows down and prevents complete draining.
The valve assembly of the present invention performs the dual function of venting the solar panel system during filling so that all air trapped in the system is permitted to escape to the atmosphere; and which also breaks any vacuum in the system during draining, and exposes the interior of the system to the atmosphere, so as to facilitate timely and complete draining of the system.